Current pipeline closures use a varying range of means to withhold the pipeline pressure and retain the door closed, including simple threaded features, interlocking bayonet style connections, large clamps, and narrow flexible compression bands. For example, U.S. Pat. Nos. 7,051,897 and 7,341,161, issued May 30, 2006 and Mar. 11, 2008 to McGuire disclose a circumferential locking member having locking segments that are either carried by a thin carrier band or by partial carrier band segments. (McGuire also discloses interconnected locking segments.) A slot segment located between opposing ends of the locking member completes the 360° pressure bearing surface, and a linkage mechanism interconnects a lever with the opposing ends. Actuating the lever effectively pulls the two ends of the locking member together so that the locking member is in a radially retracted position. The slot segment, however, is removed in a completely separate and independent action from that of the lever.
No current closure uses a single series of shear blocks to retain pipeline pressure, the shear blocks being linked together in such a way as to allow the entire assembly to retract and collapse within itself. Nor does any current closure place the holding band in communication with an operating lever such that actuating the lever results in automatic simultaneous actuation of a keystone shear block, thereby causing the holding band to expand or contract.